In mid-November, the 49ers were preparing Colin Kaepernick for his first NFL start only because Alex Smith got hurt in the previous game.

But something larger was shifting, and everybody in 49ers Universe could feel it.

In the days before that game, a Monday night special against the Chicago Bears, 49ers offensive coordinator Greg Roman couldn't predict how Kaepernick would play. But Roman had an instinct that Kaepernick could change everything.

Kaepernick happened that night, and for the rest of the season, with a rush of touchdowns and long runs and victories and tattoo-kisses.

Looking back, that move is the Big Bang of this 49ers Super Bowl push.

Once the 49ers' coaches decided to let Kaepernick compete for, and then win, the starting quarterback job, everything about this season sped up and got louder from there.

Of course, Roman is quick to point out that coach Jim Harbaugh and the 49ers staff never had a preset agenda or timetable for Kaepernick to take over from Smith.

In fact, Roman said "there's a good chance" Smith would still be the starter now if he'd never suffered the concussion against St. Louis on Nov. 11.

This all happened because Kaepernick made it happen -- in a thousand different ways.

"There wasn't a moment where we said, 'Hey, he's the guy!' " Roman said of Kaepernick. "The sun didn't come out and just start shining. It was literally a day-to-day-to-day decision."

Which makes Harbaugh's eventual decision to give the starting job to Kaepernick permanently over Smith even more intriguing. And riskier.

Now the 49ers are preparing to play Baltimore in Super Bowl XLVII next Sunday, with Kaepernick emerging as a potential superstar and the No. 1 difference-maker in this matchup.

But it was not an obvious call, if you go back to mid-November.

The 49ers were 6-2-1 after the St. Louis game, and Smith had the fifth-best passer rating in the NFL at the time.

He was completing 70 percent of his passes, expected to be healthy soon, and coming off a season in which he led the 49ers to a 13-3 record and a trip to the NFC Championship game.

"I think the numbers speak for themselves," Roman said of Smith's play up to his injury. "I think he did a good job -- really good job. I thought he played well."

The 49ers were winning with the veteran, popular Smith, and the dynamic young Kaepernick seemed to be progressing at his own pace.

The 49ers had moved up in the second round of the 2011 draft to select Kaepernick out of Nevada, and they believed in him. But, even in November, they still weren't sure if he was ready.

Kaepernick was largely a runner in college, hardly ever a drop-back passer, and the 49ers had an entrenched drop-back starter.

At the time, Kaepernick wasn't looking great in practice, and he was notably unimpressive in training camp. I asked everybody I could, and they all said the same thing -- the 49ers didn't know about Kaepernick as a starter.

But several 49ers players also pointed to one eye-opening play in the first week of the exhibition season.

Kaepernick faked a handoff to LaMichael James then took off on a breathtaking 78-yard touchdown sprint, blowing past and then bouncing off any Minnesota Vikings defender near him.

"Remember the Minnesota game? We knew what he could do," safety Donte Whitner said recently. "Ask Minnesota."

The 49ers offensive coaches felt the power of that play, too, even though it occurred in August and Kaepernick was still slated to be Smith's backup.

What a weapon he could be ...

"I always knew that was in the back pocket," Roman said of the exhibition TD. "I could pull that card out at some point if need be.

"But in this league you've got to be careful sometimes about doing things before you have to do them. Or else people adjust. You try to catch them when you can."

The time came when Smith was knocked out of the St. Louis game. Kaepernick finished that eventual tie, then Smith was ruled out for the Monday night game that followed.

That's when the long, hazy process accelerated in a blink -- just like Kaepernick on a read-option gallop.

Kaepernick's second pass of his debut start was a 22-yard laser to Vernon Davis. The strikes kept coming, Chicago seemed baffled that Kaepernick wasn't running the ball every play, and the 49ers won 32-7.

"Really, that was kind of his coming-out party in front of the whole country, and nobody knew what to expect," Roman said.

"Nobody knew. Nobody could say for sure. The bottom line is, no matter what you think is going to happen, that person has to be able to perform. And he performed. And then everything just works off that from our standpoint."

The world had changed a little: That night, Harbaugh indicated that Smith might not get the job back when he was healthy.

But with a game at New Orleans next on the schedule, the 49ers still needed to see more from Kaepernick to push him ahead of Smith, who was still limited in practice that week.

Kaepernick didn't put up dazzling numbers against the Saints, and the game largely turned on two interceptions that the 49ers returned for touchdowns.

But Kaepernick was solid (16 of 25 for 231 yards) in the 31-21 victory, held up in the crowd noise and -- most important for Harbaugh -- led a TD drive in the first series after throwing the first interception of his career.

The two games, added together, proved it all for Harbaugh and his offensive coaches.

"I think that game was big -- I mean, on the road, hostile environment, really good team," Roman said. "And he made some plays in that game that were just 'whoa' plays."

Smith was medically cleared to play the next week -- with a game at St. Louis coming up -- so now a QB decision had to be made public.

The day after the New Orleans game, Harbaugh and Roman discussed the decision, but both men knew: Kaepernick was their man. They knew they might be second-guessed, but they knew it was the right call for this moment, this season and this team.

Harbaugh broke the news to Kaepernick and Smith in a meeting that day.

"At this point, what's talk going to do?" Smith said a few days later. "I feel like he made up his mind."

The decision was not quite universally embraced in the 49ers locker room, especially among the veteran offensive players who had experienced so much with Smith.

But after the Chicago and New Orleans games, the players knew what Kaepernick could do, and they understood that Harbaugh probably knew what he was doing.

"We respected the decision that he made," Davis said recently. "A lot of guys weren't happy with it, but we had to respect it."

What gave Kaepernick the edge? In the 49ers offensive terminology, Kaepernick's explosiveness and versatility causes severe "conflicts" in the defense -- the defenders have to make instant, multiple decisions, and often Kaepernick can lure them into making critical errors.

And if they take a false step, he can go by them in an instant, or throw it to a receiver flying 50 yards down field.

Though there was no plan for a Kaepernick installation, Roman and Harbaugh had growing interest in the read-option scheme dating back to their time together at Stanford -- when they had Andrew Luck run it occasionally.

And the two coaches brought some of that philosophy to the 49ers in 2011.

"In the NFC Championship game, we did it twice," Roman said, referring to Smith running the read-option in the January 2012 loss to the New York Giants. "It worked good."

Then Roman smiled, his voice took on a singsong tone, and he added: "If Kap was in, it might've been ... "

He didn't finish the thought, but you knew what he was thinking. Roman doesn't have to wonder about that any more -- Kaepernick is the 49ers' Big Bang QB, and everything is different, faster, better.